The present invention generally relates to hydraulically entangled nonwoven composite fabrics, and more specifically, hydraulically entangled fabrics having at least three layers and containing a continuous filament and a fibrous component, and a process for making the same.
Hydraulically entangled nonwoven fabrics have many applications, such as tea bags, medical gowns, drapes, cover stock, food service, and industrial wipers. One type of hydraulically entangled nonwoven fabric may include two crimped spunbond layers sandwiching a cellulosic fiber layer. This fabric is primarily intended to be used as a launderable clothing material.
Although this fabric has advantages in applications such as clothing material, it has shortcomings in applications requiring abrasion resistance, such as, for example, industrial wipers. Consequently, using this fabric as an industrial wiper results in excessive lint particles and relatively low fabric durability. Another shortcoming is that manufacturing such fabric requires a bonding step after hydroentangling. This extra step may increase the cost of the fabric, and thus, reduce its desirability as an industrial wiper.
Accordingly, there is a need for a nonwoven fabric having at least three layers that has improved abrasion resistance and requires no additional bonding after hydroentangling.
As used herein, the term xe2x80x9ccomprisesxe2x80x9d refers to a part or parts of a whole, but does not exclude other parts. That is, the term xe2x80x9ccomprisesxe2x80x9d is open language that requires the presence of the recited element or structure or its equivalent, but does not exclude the presence of other elements or structures. The term xe2x80x9ccomprisesxe2x80x9d has the same meaning and is interchangeable with the terms xe2x80x9cincludesxe2x80x9d and xe2x80x9chasxe2x80x9d.
The term xe2x80x9cmachine directionxe2x80x9d as used herein refers to the direction of travel of the forming surface onto which fibers are deposited during formation of a material.
The term xe2x80x9ccross-machine directionxe2x80x9d as used herein refers to the direction in the same plane which is perpendicular to machine direction.
As used herein, the term xe2x80x9czonexe2x80x9d refers to a region or area set off as distinct from surrounding or adjoining parts.
As used herein, the term xe2x80x9csynthetic fiber structurexe2x80x9d such as petroleum distillates or regenerated or modified cellulosic materials. In most instances, synthetic fiber structures generally have a fiber length greater than about 0.01 meter. Examples of a synthetic fiber structure include nonwoven webs having petroleum distillate fibers, or semisynthetic regenerated cellulosic fiber structures, such as products sold under the trade designation RAYON(copyright).
As used herein, the term xe2x80x9cnonwoven webxe2x80x9d refers to a web that has a structure of individual fibers which are interlaid forming a matrix, but not in an identifiable repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes known to those skilled in the art such as, for example, meltblowing, spunbonding, wet-forming and various bonded carded web processes.
As used herein, the term xe2x80x9cspunbond webxe2x80x9d refers to a web formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries with the diameter of the extruded filaments then being rapidly reduced, for example, by fluid-drawing or other well known spunbonding mechanisms. The production of spunbond nonwoven webs is illustrated in patents such as Appel, et al., U.S. Pat. No. 4,340,563.
As used herein, the term xe2x80x9cmeltblown webxe2x80x9d means a web having fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten fibers into a high-velocity gas (e.g. air) stream which attenuates the fibers of molten thermoplastic material to reduce their diameters. Thereafter, the meltblown fibers are carried by the high-velocity gas stream and are deposited on a collecting surface to form a web of randomly disbursed fibers. The meltblown process is well-known and is described in various patents and publications, including NRL Report 4364, xe2x80x9cManufacture of Super-Fine Organic Fibersxe2x80x9d by V. A. Wendt, E. L. Boone, and C. D. Fluharty; NRL Report 5265, xe2x80x9cAn Improved Device for the Formation of Super-Fine Thermoplastic Fibersxe2x80x9d by K. D. Lawrence, R. T. Lukas, and J. A. Young; and U.S. Pat. No. 3,849,241, issued Nov. 19, 1974, to Buntin, et al., which are hereby incorporated by reference.
As used herein, the term xe2x80x9cshort fiberxe2x80x9d refers to any fiber having a length approximately less than 0.01 meter.
As used herein, the term xe2x80x9cstaple fiberxe2x80x9d refers to a cut fiber from a filament. Any type of filamenting material may be used to form staple fibers. For example, cotton, rayon, wool, nylon, polypropylene, and polyethylene terephthalate may be used. Exemplary lengths of staple fibers may be from about 4 centimeter to about 20 centimeter.
As used herein, the term xe2x80x9cfilamentxe2x80x9d refers to a fiber having a large aspect ratio.
As used herein, the term xe2x80x9cuncrimpedxe2x80x9d refers to an uncurled synthetic fiber as measured in accordance with ASTM test procedure D-3937-94 and is defined as less than two crimps per fiber.
As used herein, the term xe2x80x9ccellulosexe2x80x9d refers to a natural carbohydrate high polymer (polysaccharide) having the chemical formula (C5H10O5)n and consisting of anhydroglucose units joined by an oxygen linkage to form long molecular chains that are essentially linear. Natural sources of cellulose include deciduous and coniferous trees, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse.
As used herein, the term xe2x80x9cpulpxe2x80x9d refers to cellulose processed by such treatments as, for example, thermal, chemical and/or mechanical treatments.
As used herein, the term xe2x80x9cthermoplastic materialxe2x80x9d refers to a high polymer that softens when exposed to heat and returns to its original condition when cooled to room temperature. Natural substances exhibiting this behavior are crude rubber and a number of waxes. Other exemplary thermoplastic materials include styrene polymers and copolymers, acrylics, polyethylenes, polypropylene, vinyls, and nylons.
As used herein, the term xe2x80x9cnon-thermoplastic materialxe2x80x9d refers to any material which does not fall within the definition of xe2x80x9cthermoplastic material,xe2x80x9d above.
As used herein, the term xe2x80x9cTaber abrasionxe2x80x9d refers to values determined in substantial accordance with ASTM test procedure D-3884-92 and reported as described herein.
As used herein, the term xe2x80x9cmachine direction tensilexe2x80x9d (hereinafter may be referred to as xe2x80x9cMDTxe2x80x9d) is the force applied in the machine direction to rupture a sample in substantial accordance with TAPPI test procedure T-494 om-88 and may be reported as gram-force.
As used herein, the term xe2x80x9ccross direction tensilexe2x80x9d (hereinafter may be referred to as xe2x80x9cCDTxe2x80x9d) is the force applied in the cross direction to rupture a sample in substantial accordance with TAPPI test procedure T-494 om-88 and may be reported as gram-force.
As used herein, the term xe2x80x9cbasis weightxe2x80x9d (hereinafter may be referred to as xe2x80x9cBWxe2x80x9d) is the weight per unit area of a sample calculated in accordance with ASTM test procedure D-3776-96, Option C, and may be reported as gram-force per meter squared.
As used herein, the term xe2x80x9cgauge lengthxe2x80x9d is the sample length, typically reported in centimeters, measured between the points of attachment. As an example, a fabric sample is tautly clamped in a pair of grips. The initial distance between the grips, generally about 7.6 or 10.2 centimeters, is the gauge length of the sample.
As used herein, the term xe2x80x9cpercent stretchxe2x80x9d refers to values determined as described herein.
As used herein, the term xe2x80x9ctrap tearxe2x80x9d refers to values determined in general accordance with TAPPI test procedure T 494 om-88 as described herein.
The problems and needs described above are addressed by the present invention, which desirably provides a fabric including a synthetic fiber structure first zone, a synthetic fiber structure second zone, and a short fiber third zone. The first zone may include a spunbond web layer and a meltblown web layer. The synthetic fiber structure second zone may be positioned proximate to the synthetic fiber structure first zone and the short fiber third zone may be positioned substantially between the first and second zones. Desirably, at least a portion of the first and second zones may be entwined with the third zone.
In addition, the short fiber third zone may include pulp fibers, staple fibers, particulates, and combinations of one or more thereof. Furthermore, the second zone may include a spunbond web layer and a meltblown web layer. Moreover, the first and second zones may be prebonded prior to being entwined.
In another embodiment, the short fiber third zone may include a plurality of cellulosic material layers. The synthetic fiber structure second zone may be positioned proximate to the synthetic fiber structure first zone and the short fiber third zone may be positioned substantially between the first and second zones. Desirably, at least a portion of the first and second zones may be entwined with the third zone.
Furthermore, the short fiber third zone may include three cellulosic material layers. In addition, the short fiber third zone may include pulp and staple fibers or particulates. Moreover, the first or second zone may include a spunbond web layer and a meltblown web layer.
A further embodiment of the present invention may be a process for producing a fabric. The process may include the steps of providing a prebonded synthetic fiber structure first zone, providing a synthetic fiber structure second zone, and providing a short fiber third zone. The third zone may be positioned substantially between the first and second zones. Desirably, the first and second zones may be hydroentangled.
Additionally, the short fiber third zone may include pulp fibers, staple fibers, or pulp fibers and staple fibers. Moreover, the second zone may include a spunbond web layer and a meltblown web layer.
In a further embodiment, the fabric may have a Taber abrasion value of not less than about 3 in substantial accordance with ASTM test procedure D-3884-92.
Furthermore, the short fiber third layer may include pulp fibers, staple fibers, pulp and staple fibers, and particulates. Desirably, the first layer is a nonwoven web layer, and more desirably, the nonwoven web layer is a spunbond web layer. Moreover, the first and second layers may be prebonded prior to being entwined.
Another embodiment of the present invention may be a fabric having a short fiber and a weight loss less than about 6 percent after 5 washing and drying cycles.
In yet a further embodiment, the first zone may include uncrimped fibers.
In a still further embodiment, the fabric may include a prebonded synthetic fiber structure first zone.